Differential effects of fat deficiency on hepatic and pulmonary drug metabolizing enzymes in rat and mouse

In the present study, we have evaluated the effect of dietary fat deprivation on the carcinogen/drug metabolizing enzymes in rats and mice. In rats, hepatic AHH, Cyt.P-450 Cyt.b5 and Cyt.c-reductase were significantly decreased due to fat deficiency, whereas in lungs, AHH and Cyt.c-reductase were decreased without any change in Cyt.P-450 level. In mice, feeding of fat-free diet did not cause any alteration in hepatic AHH and Cyt.P-450, but the levels of Cyt.b5 and Cyt.c-reductase were significantly reduced. In contrast to liver, Cyt.P-450 and Cyt.b5 were increased in lungs. Activity of UDPGT was lowered both in liver and lungs of rats whereas GST and GSH were increased in liver only. In mice, a decrease in UDPGT and appreciable increases in GST and GSH in liver were observed. However, in lungs, UDPGT activity was enhanced by feeding fat-free diet. These observations suggest that mice and rats respond differentially to the depletion of fat in the diet.     

Predicted secondary structure of maltodextrin Phosphorylase fromEscherichia coli as deduced using Chou-Fasman model

Secondary structure of maltodextrin Phosphorylase fromEscherichia coli has been predicted using Chou-Fasman model. The enzyme protein contains 28% α-helix, 27% β-pleated sheets and 20% reverse β-turns. The secondary structure predicted 4 regions showing Rossman-fold super secondary structure. Two regions, one from residue 268–361 and the another from residue 606–684, having 4 consecutive strands of parallel β-pleated sheets and 3 joining α-helix, are predicted. Two regions, one from residue 379–434 and the another from residue 496–573, having 3 consecutive strands of parallel β-pleated sheets and two joining α-helix, are predicted.     

Distribution of constitutive heterochromatin in Hela and HEp-2 cell lines

Summary Despite the fact that HeLa and HEp-2 cell lines have been established respectively from a female and a male patient, the frequent loss of the Y chromosome makes it difficult to discriminate the two cell types. The technique of centromeric localization of heterochromatin, however, facilitates more definite identification of the two cell types. Giemsa positive centromeric constitutive heterochromatin blocks were induced within the intact metaphase chromosome preparations of Hela and HEp-2 cells. The Hela cell population had a single heterochromatin marker chromosome, whereas the HEp-2 cell line was found to possess two types of heterochromatin markers. The distinctive patterns of distribution of constitutive heterochromatin of these three chromosomes served as the guides in tracing the presumptive cytological pathways for their orgin.

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Zusammenfassung Trotz der Tatsache, daß Hela- und HEp-2-Zellinien jeweils von einem weiblichen und einem männlichen Patienten stammen, erschwert der häufige Verlust des Y-Chromosoms eine Unterscheidung der beiden Zelltypen. Der Nachweis des zentromernahen Heterochromatins jedoch ermöglicht eine zuverlässigere Erkennung dieser beiden Zelltypen. Die Hela-Zellpopulation hat ein einzelnes, durch das Heterochromation gekennzeichnetes Marker-Chromosom, während die HEp-2-Zellinie deren 2 besitzt. Das distinkte Verteilungsmuster des konstitutiven Heterochromatons dieser 3 Chromosomen dient dazu, die vermutliche cytologische Herkunft zu interpretieren.

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Supported in part by the Robert A. Welch Foundation, The National Foundation —March of Dimes and USPHS Grant No. FR-05425.     

Constitutive heterochromatin patterns of G-group chromosomes in Down's syndrome

Summary 2 male patients with G-trisomic Down's syndrome, were studied for constitutive heterochromatin pattern by the technique of Arrighi and Hsu (1971). 2 G-chromosomes were found to have heterochromatin distributed around the centromeric areas and the remaining 3 were free of such localized heterochromatin blocks; the extra G-chromosome belonging to the non-localized heterochromatin members.

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Zusammenfassung 2 männliche Patienten mit G-Trisomie (Down-Syndrom) sind im Hinblick auf das konstitutive Heterochromatinmuster mit Hilfe der Technik von Arrighi u. Hsu (1971) untersucht worden. Es fanden sich 2 G-Chromosomen, die eine Heterochromatinverteilung um die Zentromerregion zeigen, während die restlichen 3 frei von derartig lokalisierten Heterochromatinblocks sind; das überzählige G-Chromosom gehört zu den letztgenannten.

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Supported in part by the Robert A. Welch Foundation, The National Foundation —March of Dimes and USPHS Grant No. FR-05425.     

Regulation of Cerebroside and Sulfatide Metabolism in Glia Cells

Mouse oligodendroglioma cells, G-26 clone 20 and 24, contain galactosylceramide (cerebroside) and sulfogalactosylceramide (sulfatide) as determined by an HPLC technique. The synthesis of both these lipids was stimulated by 10(-6) M hydrocortisone (cortisol) and also by the removal of serum from the culture medium. Forty-eight hours after the addition of cortisol the incorporation of H235SO4 into sulfatide, the level of sulfatide and the specific activity of the enzyme 3'-phosphoadenosine 5'-phosphosulfate:galactosylceramide sulfotransferase in the cells increased three- to fourfold. The level of cerebroside and the specific activity of UDP-galactose:hydroxyacyl sphingosine galactosyltransferase also increased threefold in the cells on treatment with cortisol. The effect of the hormone on the synthesis of cerebroside preceded the increase in sulfatide synthesis. Experiments with cycloheximide and actinomycin D showed that the effect of the hormone on glycolipid synthesis in these cells were mediated through de novo messenger RNA and protein synthesis. Removal of serum from the culture medium resulted in an approximately twofold enhancement of H235SO4 incorporation into sulfatide within 24 h. The levels of sulfatide and cerebroside and the specific activity of the galactosyltransferase and sulfotransferase also increased significantly after serum removal. However, in contrast to the effect of the steroid, the sulfotransferase activity and the level of sulfatide increased prior to elevations in galactosyltransferase and cerebroside. The effect of serum removal was also found to be mediated by de novo RNA and protein synthesis. The effects of cortisol and serum removal on the synthesis of cerebroside and sulfatide were strictly additive.     

Genetic diversity among Plantagos V. Transmission of the additional chromosome in a triplo-4 individual ofPlantago lagopus L.

In crosses betweenP. lagopus trisomic for chromosome 4 and normal disomics the extra chromosome is transmitted to about 1/4 of the progeny through the male side and to over 1/2 on the female side. Among the progeny some non-parental types which include a tetrasomic (2x + 2) and an aneutriploid (3x + 1) were also found. Chromosomal behaviour during their male meiosis is described.     

Analyses for in vitro growth conditions,cytokinetics, and sister chromatid exchanges in lymphocytes cultured from the Sprague-Dawley rat

Summary Peripheral blood samples from Sprague-Dawley rats gave successful lymphocyte growth in GIBCO: IA, RPMI 1640, and Eagle's minimum essential medium (MEM) culture media. Various growth conditions, cytokinetics, and sister chromatic exchange (SCE) induction were studied using reconstituted GIBCO 1A only. Neither methoxyflurane anesthesia of the rats before sampling nor washing of the cells with phosphate buffered saline affected the mitotic index. Cultures treated with [³H]thymidine showed the lymphocytes entering into DNA synthesis after approximately 24 h. The time at which BUdR (5-bromo-2′ deoxyuridine) was added, i.e. 0 vs. 24 h incubation, had minimal effect on the mitotic index of cultures harvested at 48 h. However, when harvest was extended to 72 h, mitotic activity was greater in the cultures treated with BUdR at 24 h. No significant differences in mitotic index and the number of average lymphocyte division were detected in cultures exposed to 0.3 to 0.5 μg/ml BUdR at 24 h and harvested at 72 h. Although SCE frequencies increased in the presence of BUdR, the baseline level of SCEs was estimated to be 5 to 6/cell. Average generation time of the lymphocytes dividing between 48 and 72 h was 16.5 h. Because of its simplicity of culture and the reproducible nature of its in vitro growth kinetics, the Sprague-Dawley rat lymphocyte is a suitable model for cytogenetic investigations.     

Two complementary radiometric methods for the measurement of 5-amino-4-imidazole-N-succinocarboxamide ribonucleotide synthetase (SAICAR synthetase)

Two complementary methods have been devised for measuring the activity of 5-amino-4-imidazole-N-succinocarboxamide ribonucleotide synthetase (SAICAR synthetase, EC 6.3.2.6), a critical enzyme in the pathway of purine biosynthesis. In the first method, l-[4.¹⁴C]aspartic acid is condensed with 5-amino-4-imidazolecarboxylic acid ribonucleotide (AICOR) via the action of SAICAR synthetase. Unreacted l-[4-¹⁴C]aspartic acid is measured by scintillation spectrometry. In the second method, the reverse reaction of SAICAR synthetase is measured; radiactive 5-amino-4-imidazole-N-succinocarboxamide ribonucleotide (SAICAR) is synthetized enzymatically, using a partial purified preparation of SAICAR synthetase from chicken liver. To the purified [¹⁴C]SAICAR is added: sodium arsenate, Tris-HCl buffer containing ADPMgCl₂ or buffer alone, and to initiate the reaction, a 12 000 × g supernatant or other suitable source of enzyme. As a consequence of the arsenolytic cleavage of [¹⁴C]SAICAR, l-[4-¹⁴C]aspartic acid is generated in stoichiometric amounts. The fourth carbon of this amino acid is then detached by selective enzymatic decarboxylation, trapped in 40% KOH and quantitated by scintillation spectrometry. The assays, performed as prescribed, are facile and notably sensitive; using them, the specific activity of SAICAR synthetase has been measured in acetone powders of the livers of representative members of the Vertebrata, and also in the principal viscera of the mouse. Of the livers examined, pigeon liver was the richest source of the investigated enzyme.     

Biofilm diatom community structure: influence of temporal and substratum variability

Diatoms, which are early autotrophic colonisers, are an important constituent of the biofouling community in the marine environment. The effects of substratum and temporal variations on the fouling diatom community structure in a monsoon-influenced tropical estuary were studied. Fibreglass and glass coupons were exposed every month for a period of 4 days and the diatom population sampled at 24 h intervals, over a period of 14 months. The planktonic diatom community structure differed from the biofilm community. Pennate diatoms dominated the biofilms whilst centric diatoms were dominant in the water column. Among the biofilm diatoms, species belonging to the genera Navicula, Amphora, Nitzschia, Pleurosigma and Thalassionema were dominant. On certain occasions, the influence of planktonic blooms was also seen on the biofilm community. A comparative study of biofilms formed on the two substrata revealed significant differences in density and diversity. However species composition was almost constant. In addition to substratum variations, the biofilm diatom community structure also showed significant seasonal variations, which were attributed to physico-chemical and biological changes in both the water and substratum. Temporal variations in the tychopelagic diatoms of the water were also observed to exert an influence on the biofilm diatom community. Variations in diatom communities may determine the functional ecosystem of the benthic environment.